Fishes, aquatic vertebrates, breathing by gills. They are very numerous, and are of interest to the sportsman as game, to people in general as food and to the scientific student. Excluding the lancet and the Cyclostomata as below the true fishes, there are four orders left. 1. Bony or modern fishes (Teleostei). This is far the largest group, including most of the food and game fishes both in fresh and salt water, as cod, bass, perch, pike, trout, mackerel, etc. 2. Ganoid or ancient armored fishes (Ganoidei), including fishes with shiny hard scales, like the garpike, sturgeon, bowfin, etc. Representatives of this order are found as fossils in very ancient rocks, while the first order occurs as fossils only in relatively modern rocks. 3. Mudfishes, or double breathers (Dipnoi), including fishes that possess both gills and lungs, being the lowest vertebrates to have lungs. These first lungs are formed from the air-bladder, which is interesting, as it gives us a clue to the origin of lungs. These fishes live in the waters of Africa and Australia that dry up, and they form for themselves mud cases in which they live till the water returns again. The heart is imperfectly three-chambered, and by this and the possession of lungs they are closely allied to the Amphibia. 4. Cartilaginous fishes (Elasmobranchii), fishes with a cartilaginous skeleton and brain-case, instead of a bony one, including sharks, rays, skates, torpedoes, etc.
Fishes make a natural group or class. They have a two-chambered heart, consisting of an auricle and ventricle. They have gills and blood vessels running in the gill-arches that are called aortic arches—usually four or five in number. These run around the pharynx and unite above into the aorta or great artery. The blood is sent out from the heart to the gills; there it takes in oxygen and continues its circulation as arterial blood; and, passing through the capillaries of the body, it returns to the heart as venous blood. Fish have fins, supported by fin-rays, for swimming. Their colors vary, and often are brighter during the spawning season. Their food is diverse, many of them eating smaller fishes, crustacea and worms, while others feed upon plants; some few swallow mud for the sake of the organic matter contained in it. Their eggs are usually laid in immense numbers; for example, the whitefish or trout lays about 50,000 eggs in one season. Some forms, like sharks, lay few eggs, which are either retained within the body till hatched, or, in closely related species, are laid in the water, enveloped in a horny case. The horny cases of skates and sharks are called mermaid-purses. Some forms, like sticklebacks, build nests and care for the eggs until hatched. All fishes possess a set of sense-organs that are fitted to receive vibrations from the water, called the sense-organs of the lateral line. If any common fish be examined, there will be seen a line running on each side about the middle of the body. This is the position of the lateral line. These organs exist also in the tadpole stages of frogs and toads, but disappear when the animals leave the water, and are not present in land animals. Deep-sea explorations have brought to light many strange and curious fishes, some of them having luminous spots, from which light is emitted. See Blindfish, Carp, Cod, Goldfish and others in alphabetical order. See Goode's American Fishes; Baskett's The Story of the Fishes; and Jordon's Fishes (1907).
Fishhawk or Osprey, a common well-known bird of eagle-like appearance, found in all countries, except Iceland and New Zealand. It is abundant in the United States along the Atlantic, and is also found inland in the vicinity of water. The American osprey is about two feet long; brownish above and whitish below; the upper part of the beak is strongly curved over the lower, and the claws are long and sharp, being especially formed for grasping. These birds feed exclusively on fish, and are expert fishers. They fly to and fro above the water and make a sudden dash after fish near the surface, sometimes going into the water to a depth of about one and one half feet. Their feathers are compact and oily, and do not become wet. The bald-headed eagle often chases the osprey, and robs it of its fish while in the air. In America the osprey nests on large trees, in Europe on rocky cliffs. The great nest is built of sticks, sea-weed and other material, and is used year after year. The two to four eggs vary in color, sometimes being white, again buff or chocolate. Ospreys mate for life, show much family affection, often make of the nest an all-year-home.
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| JOHN FISKE |
Fiske, John, an American author and historian, was born March 30, 1842, at Hartford, Conn. Graduating from Harvard in 1863, he became known as a deep thinker and forcible writer. In 1861 he made his mark with a notable critique on the fallacies in Buckle's history of English civilization. From 1869 to 1879 he was at Harvard, first as a brilliant lecturer on philosophy, then as assistant-libra-
